The present invention relates to an apparatus for removing liquid from an air-liquid separator, more specifically such a device which eliminates the need for a separate pump in the liquid outlet line.
In low gravity or zero gravity environments, air is used to entrain and transport initially uncontained liquid. The air-liquid mixture must then be separated and the components returned to their systems for use. Cyclone or vortex-type separators are ideal for this application when large volumes of liquid or air are involved. Rotary dynamic-type separators are presently used for small volumes (less than 50 cfm of air and 1 gpm of liquid).
Vortex-type separators are well known in the art and typically comprise a generally cylindrical housing having a conically shaped bottom end wherein the air-liquid mixture is introduced into the upper portion of the housing via a generally tangentially extending inlet conduit. The circular motion of the mixture causes the heavier liquid to accumulate on the walls of the housing and drop to the conical bottom of the separator. The separated air is withdrawn from the center of the housing via an air outlet tube. The water collecting at the bottom of the housing must be removed for the device to be in continuous use.
One of the present ways of removing this accumulated liquid is to have a pump in a liquid outline line communicating with the water collecting sump. The operation of the pump is controlled by electrode sensors in the conical sump section of the vortex separator which senses when the water has accumulated to a predetermined level. Once the water reaches this level, the pump is turned on and the water pumped out of the separator. The "on" condition of the pump is timed to the volume of liquid to be discharged from the sump.
While generally successful, these systems do suffer from serious drawbacks. The electrode sensors, since they contact the water will eventually degrade, thereby rendering them ineffective or inaccurate. Also, the sensors can be fooled by the presence of air bubbles in the water to improperly indicate that no water is present. Also, this system cannot easily be related to a desired flowrate, since the pump is usually either "on" or "off". possible presence of dirt or debris in the liquid, which would, at least, result in excessive wear of the gear pumps or possibly, render them totally ineffective. Centrifugal pumps cannot be utilized because it is possible to lose the priming fluid, thereby rendering them totally ineffective.